Method of interconnecting a coaxial connector to a coaxial cable via ultrasonic welding

ABSTRACT

A coaxial connector for interconnection with a coaxial cable with a solid outer conductor by ultrasonic welding is provided with a monolithic connector body with a bore. An annular flare seat is angled radially outward from the bore toward a connector end of the connector; the annular flare seat open to the connector end of the connector. The flare seat may be provided with an annular flare seat corrugation.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of commonly owned co-pendingU.S. Utility patent application Ser. No. 12/951,558, titled “Laser WeldCoaxial Connector and Interconnection Method”, filed Nov. 22, 2010 byRonald A. Vaccaro, Kendrick Van Swearingen, James P. Fleming, James J.Wlos and Nahid Islam, currently pending and hereby incorporated byreference in its entirety.

BACKGROUND

1. Field of the Invention

This invention relates to electrical cable connectors. Moreparticularly, the invention relates to a coaxial cable connectorinterconnectable with a coaxial cable via ultrasonic welding.

2. Description of Related Art

Coaxial cable connectors are used, for example, in communication systemsrequiring a high level of precision and reliability.

To create a secure mechanical and optimized electrical interconnectionbetween the cable and the connector, it is desirable to have generallyuniform, circumferential contact between a leading edge of the coaxialcable outer conductor and the connector body. A flared end of the outerconductor may be clamped against an annular wedge surface of theconnector body via a coupling body. Representative of this technology iscommonly owned U.S. Pat. No. 6,793,529 issued Sep. 21, 2004 to Buenz.Although this type of connector is typically removable/re-useable,manufacturing and installation is complicated by the multiple separateinternal elements required, interconnecting threads and relatedenvironmental seals.

Connectors configured for permanent interconnection via solder and/oradhesive interconnection are also well known in the art. Representativeof this technology is commonly owned U.S. Pat. No. 5,802,710 issued Sep.8, 1998 to Bufanda et al. However, solder and/or adhesiveinterconnections may be difficult to apply with high levels of qualitycontrol, resulting in interconnections that may be less thansatisfactory, for example when exposed to vibration and/or corrosionover time.

Competition in the coaxial cable connector market has focused attentionon improving electrical performance and long term reliability of thecable to connector interconnection. Further, reduction of overall costs,including materials, training and installation costs, is a significantfactor for commercial success.

Therefore, it is an object of the invention to provide a coaxialconnector and method of interconnection that overcomes deficiencies inthe prior art.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate embodiments of the invention,where like reference numbers in the drawing figures refer to the samefeature or element and may not be described in detail for every drawingfigure in which they appear and, together with a general description ofthe invention given above, and the detailed description of theembodiments given below, serve to explain the principles of theinvention.

FIG. 1 is a schematic external isometric view of an exemplary embodimentof a coaxial connector installed upon a coaxial cable with a couplingnut spaced away from the connector along the cable forconnector-to-cable interconnection.

FIG. 2 is a schematic isometric view of the coaxial connector of FIG. 1installed upon a coaxial cable, with the coupling nut seated upon thecoaxial connector.

FIG. 3 is a schematic isometric view of the coaxial connector of FIG. 1.

FIG. 4 is a schematic partial cross section side view of the connectorof FIG. 2.

FIG. 5 is an enlarged view of area A of FIG. 4.

FIG. 6 is a schematic exploded isometric partial cut-away view of theconnector and cable of FIG. 1.

FIG. 7 is a schematic cross section side view of an alternativeembodiment of a coaxial connector with a corrugated flare seat.

FIG. 8 is an enlarged view of area C of FIG. 7.

FIG. 9 is a schematic partial cut-away isometric view of the connectorof FIG. 7.

FIG. 10 is a schematic isometric cut-away view of the overbody of FIG.5.

FIG. 11 is a schematic isometric partial cut-away view of the connectorbody of FIG. 5.

FIG. 12 is a schematic isometric view of an alternative connector bodywith notches on a flange of the connector body.

FIG. 13 is a schematic isometric view of an alternative connector bodywith longitudinal knurls on the connector body outer diameter.

FIG. 14 is an enlarged view of area B of FIG. 4.

FIG. 15 is a schematic cross section side view of an alternativeoverbody with corrugation on an inner diameter of the cable end.

FIG. 16 is a schematic cross section side view of an alternativeoverbody with a stepped surface on an inner diameter of the cable end.

FIG. 17 is a schematic cross section side view of a coaxial connectorembodiment with an inner conductor end cap.

DETAILED DESCRIPTION

Aluminum has been applied as a cost-effective alternative to copper forthe conductors in coaxial cables. However, aluminum oxide surfacecoatings quickly form upon air-exposed aluminum surfaces. These aluminumoxide surface coatings may degrade traditional mechanical, solder and/orconductive adhesive interconnections.

The inventors have recognized that increasing acceptance of coaxialcable with solid outer conductors of aluminum and/or aluminum alloyenables connectors configured for interconnection via ultrasonic weldingbetween the outer conductor and a connector body which may also be costeffectively provided, for example, formed from aluminum and/or aluminumalloy.

An ultrasonic weld may be formed by applying ultrasonic vibrations underpressure in a join zone between two parts desired to be welded together,resulting in local heat sufficient to plasticize adjacent surfaces thatare then held in contact with one another until the interflowed surfacescool, completing the weld. An ultrasonic weld may be applied with highprecision via a sonotrode and/or simultaneous sonotrode ends to a pointand/or extended surface. Where a point ultrasonic weld is applied,successive overlapping point welds may be applied to generate acontinuous ultrasonic weld.

Exemplary embodiments of an ultrasonic weldable coaxial connector 2 aredemonstrated in FIGS. 1-17. As best shown in FIG. 4, a unitary connectorbody 4 is provided with a bore 6 dimensioned to receive the outerconductor 8 of a coaxial cable 9 therein. As best shown in FIG. 5, aflare seat 10 angled radially outward from the bore 6 toward a connectorend 18 of the connector body 4 is open to the connector end of thecoaxial connector 2 providing a mating surface to which a leading endflare 16 of the outer conductor 8 may be ultrasonically welded by thesonotrode of an ultrasonic welder.

One skilled in the art will appreciate that connector end 18 and cableend 12 are applied herein as identifiers for respective ends of both theconnector and also of discrete elements of the connector describedherein, to identify same and their respective interconnecting surfacesaccording to their alignment along a longitudinal axis of the connectorbetween a connector end 18 and a cable end 12.

Prior to interconnection via ultrasonic welding, the leading end of thecoaxial cable 9 may be prepared, as best shown in FIG. 6, by cutting thecoaxial cable 9 so that the inner conductor 24 extends from the outerconductor 8. Also, dielectric material 26 between the inner conductor 24and outer conductor 8 may be stripped back and a length of the outerjacket 28 removed to expose desired lengths of each. The cable end 12 isinserted through the bore 6 and an annular flare operation performed ona leading edge of the outer conductor 8; the resulting leading end flare16 may be angled to correspond to the angle of the flare seat 10 withrespect to a longitudinal axis of the coaxial connector 2. By performingthe flare operation against the flare seat 10, the resulting leading endflare 16 can be formed with a direct correspondence to the flare seat 10angle.

The flare seat 10 may alternatively be formed with surface features,such as a flare seat corrugation 14, demonstrated for example in FIGS.7-9 as an annular corrugation. Surface features provide increasedsurface area along which the ultrasonic weld may be applied, increasingthe strength of the resulting interconnection, without requiring acorresponding increased diameter of the leading end flare 16 which mayhave a negative impact on an impedance discontinuity characteristic ofthe resulting coaxial connector interconnection. Further surfacefeatures may include, for example, annular or radial knurls or otherprotrusion configurations.

Ultrasonic welding may be performed, for example, utilizing torsionalvibration. In torsional vibration ultrasonic-type friction welding, atorsional vibration is applied to the interconnection via a sonotrodeapplied to the cable end 12 of the leading end flare 16, while thecoaxial connector 2 and flare seat 10 therewithin are held static. Thetorsional vibration generates a friction heat which plasticizes thecontact surfaces between the leading end flare 16 and the flare seat 10.Where torsional vibration ultrasonic-type friction welding is utilized,a suitable frequency and torsional vibration displacement, for examplebetween 20 and 40 KHz and 20-35 microns, may be applied.

Because the localized abrasion of the ultrasonic welding process canbreak up any aluminum oxide surface coatings in the immediate weld area,no additional care may be required with respect to removing or otherwisemanaging the presence of aluminum oxide on the interconnection surfaces.

An overbody 30, as shown for example in FIG. 10, may be applied to theconnector body 4 as an overmolding of polymeric material. The overbody30 increases cable to connector torsion and pull resistance. Theoverbody 30 may also provide connection interface structure at theconnector end 18 and further reinforcing support at the cable end 12,enabling significant reductions in the size of the connector body 4,thereby reducing overall material costs.

Depending upon the applied connection interface 31, demonstrated in theexemplary embodiments herein as a standard 7/16 DIN interface, theoverbody 30 may be provided with an overbody flange 32 and longitudinalsupport ridges 34 for a coupling nut 36. The coupling nut 36 is retainedupon the support ridges 34 at the connector end 18 by an overbody flange32 and at the cable end 12 by a retention spur 38 provided on at leastone of the support ridges 34. The retention spur 38 may be angled towardthe connector end 18, allowing the coupling nut 36 to be placed over thecable 9 initially spaced away from the coaxial connector 2 duringinterconnection (see FIG. 1), but then allowing the coupling nut 36 tobe passed over the retention spur 38 and onto the support ridges 34 fromthe cable end 12, to be thereafter retained upon the support ridges 34by the retention spur(s) 38 (see FIG. 2) in close proximity to theconnector interface 31 for connector to connector mating. The supportridges 34 reduce polymeric material requirements of the overbody 30while providing lateral strength to the connector/interconnection 2 aswell as alignment and retention of the coupling nut 36.

The overbody 30 may also extend from the connector end 18 of theconnector body 4 to provide portions of the selected connector interface31, such as an alignment cylinder 39 of the 7/16 DIN interface, furtherreducing metal material requirements of the connector body 4.

The overbody flange 32 may be securely keyed to a connector body flange40 of the connector body 4 and thereby with the connector body 4 via oneor more interlock apertures 42 such as holes, longitudinal knurls 43,grooves, notches 45 or the like provided in the connector body flange 40and/or outer diameter of the connector body 4, as demonstrated in FIGS.11-13. Thereby, as the polymeric material of the overbody 30 flows intothe interlock apertures 42 during overmolding, upon curing the overbody30 is permanently coupled to and rotationally interlocked with theconnector body 4.

As best shown in FIG. 14, the cable end 12 of the overbody 30 may bedimensioned with an inner diameter friction surface 44 proximate that ofthe coaxial cable outer jacket 28, enabling polymeric friction weldingbetween the overbody 30 and the outer jacket 28, as the connector body 4and outer conductor are rotated with respect to each other, therebyeliminating the need for environmental seals at the cable end 12 of theconnector/cable interconnection. During friction welding, the coaxialconnector 2 is rotated with respect to the cable 9. Friction between thefriction surface 44 and the outer diameter of the outer jacket 28 heatsthe respective surfaces to a point where they begin to soften andintermingle, sealing them against one another. The outer jacket 28and/or the inner diameter of the overbody 30 may be provided as a seriesof spaced apart annular peaks of a contour pattern such as a corrugation46, as shown for example in FIG. 15, or a stepped surface 48, as shownfor example in FIG. 16, to provide enhanced friction, allow voids forexcess friction weld material flow and to add key locking for additionalstrength. Alternatively, the overbody 30 may be sealed against the outerjacket 28 with an adhesive/sealant or may be overmolded upon theconnector body 4 after interconnection with the outer conductor 8, theheat of the injected polymeric material bonding the overbody 30 withand/or sealing against the outer jacket 28.

The inner conductor 24 extending from the prepared end of the coaxialcable 9 may be selected to pass through to the connector end 18 as aportion of the selected connection interface 31, for example as shown inFIG. 4. If the selected coaxial cable 9 has an inner conductor 24 thathas a larger diameter than the inner conductor portion of the selectedconnector interface 31, the inner conductor 24 may be ground at theconnector end 18 to the required diameter.

Although a direct pass through inner conductor 24 advantageouslyeliminates interconnections, for example with the spring basketinterconnection with a traditional coaxial connector inner contact, suchmay introduce electrical performance degradation such as PIM. Where theinner conductor 24 is also aluminum material some applications mayrequire a non-aluminum material connection point at the innercontact/inner conductor of the connection interface 31. As shown forexample in FIG. 17, a center cap 50, for example formed from a metalsuch as brass or other desired metal, may be applied to the end of theinner conductor 24, also by friction or ultrasonic welding. To apply thecenter cap 50, the end of the inner conductor 24 is ground to provide apin corresponding to the selected socket geometry of the center cap 50.To allow material inter-flow during welding attachment, the socketgeometry of the center cap 50 and or the end of the inner conductor 24may be formed to provide material gaps.

One skilled in the art will appreciate that the connector andinterconnection method disclosed has significant material costefficiencies and provides a permanently sealed interconnection withreduced size and/or weight requirements.

Table of Parts 2 coaxial connector 4 connector body 6 bore 8 outerconductor 9 cable 10 flare seat 12 cable end 14 flare seat corrugation16 leading end flare 18 connector end 20 bore sidewall 24 innerconductor 26 dielectric material 28 outer jacket 30 overbody 31connection interface 32 overbody flange 34 support ridge 36 coupling nut38 retention spur 39 alignment cylinder 40 connector body flange 42interlock aperture 43 longitudinal knurl 44 friction surface 45 notch 46corrugation 48 stepped surface 50 center cap

Where in the foregoing description reference has been made to materials,ratios, integers or components having known equivalents then suchequivalents are herein incorporated as if individually set forth.

While the present invention has been illustrated by the description ofthe embodiments thereof, and while the embodiments have been describedin considerable detail, it is not the intention of the applicant torestrict or in any way limit the scope of the appended claims to suchdetail. Additional advantages and modifications will readily appear tothose skilled in the art. Therefore, the invention in its broaderaspects is not limited to the specific details, representativeapparatus, methods, and illustrative examples shown and described.Accordingly, departures may be made from such details without departurefrom the spirit or scope of applicant's general inventive concept.Further, it is to be appreciated that improvements and/or modificationsmay be made thereto without departing from the scope or spirit of thepresent invention as defined by the following claims.

We claim:
 1. A method for interconnecting a coaxial connector with asolid outer conductor coaxial cable, comprising the steps of: providinga monolithic connector body with a bore; a flare seat angled radiallyoutward from the bore toward a connector end of the connector; insertinga leading end of the coaxial cable into the bore, until a leading end ofthe solid outer conductor extends beyond the flare seat; flaring theleading end of the solid outer conductor to provide a flare of the outerconductor adjacent the flare seat; ultrasonically welding the flare tothe flare seat.
 2. The method of claim 1, wherein the outer conductorand the connector body are each one of aluminum and aluminum alloymaterial.
 3. The method of claim 1, wherein the flare seat and the flareof the outer conductor have the same angle.
 4. The method of claim 1,wherein a vibration and longitudinal force are applied until heatedsufficiently to plasticize a surface of the flare seat and the flare ofthe outer conductor into one another.
 5. The method of claim 1, furtherincluding rotation of the connector body with respect to the coaxialcable to create a friction weld between the outer conductor and theconnector body.
 6. The method of claim 1, further including the step ofovermolding the connector body attached to the end of the coaxial cablewith a polymeric overbody.
 7. The method of claim 1, further includingthe steps of preparing the leading end of the cable end prior toinsertion into the bore by removing a portion of the outer conductor sothat an inner conductor extends therefrom, removing a portion of adielectric material between the inner conductor and the outer conductorsuch that when the leading edge of the outer conductor extends under theflare seat, a flare tool does not contact the dielectric material; andstripping back a portion of a jacket from the outer conductor.
 8. Themethod of claim 1, further including providing an overbody of polymericmaterial upon an outer diameter of the connector body, the overbodyextending from the cable end of the connector body, an inner diameter ofthe overbody extending from the cable end of the connector body providedas a friction surface dimensioned for an interference fit upon an outerdiameter of a jacket of the coaxial cable.
 9. The method of claim 8,wherein rotation of the connector body with respect to the coaxial cableforms a friction weld between the outer conductor and the connector bodyand between the overbody and the jacket of the coaxial cable.